Insulated tank assemblies such as water heaters have long been known in the art. Such structures typically comprise an inner storage tank or vessel and an outer shell or jacket. Typically, both the inner storage tank and outer jacket are cylindrical in shape. Typically the jacket is coaxial with and radially spaced from the tank so that an annular space or void is formed there between. A polymer foam insulating material is commonly provided in at least a portion of this annular space to provide thermal insulation for the liquid held in the storage tank.
A particularly effective insulating material for this purpose is a polymer foam that is expanded directly in the annular space between the inner tank and jacket. Various types of epoxy and polyolefin foams have been utilized for this purpose and polyurethane foam has been found to be particularly effective.
As is known to those skilled in the art, a polymer reactive composition is injected into the void or space between the tank and jacket and the resulting foam expands to fill the available space. The polymer foam is initially fluid and sticky. It, however, slowly expands to fill substantially all the space between the tank and jacket. As the polymerization reaction reaches its completion the polymer foam becomes stiff and stabilizes into a rigid, closed cell foam that fills the annular space surrounding the tank and forms a thermal insulation for the liquid held in the tank. The amount of liquid polymer reactant composition injected into the annular space is only sufficient to ensure that the annular space is filled with polymer foam without creating excessive over-pressure in the space.
Water heater tanks incorporate a number of inlet, outlet and drain fittings. A gas water heater includes a heating chamber at the bottom of the tank. Specifically, a gas burner is positioned in the heating chamber and water in the tank is heated with a flame from the burner. The tank also includes sensors for thermostatic control so that the water in the tank is maintained at a desired temperature.
Many polymer foams used for insulation purposes are flammable and, accordingly, they must be maintained a safe distance from the open burner flame of the heating chamber.
It is presently common practice to provide a foam dam device in place in the annular space between the inner tank and outer jacket at a selected position along the height of the cylindrical inner tank. More specifically, the foam dam is compressed between the outer wall of the inner tank and the inner wall of the outer jacket so as to seal the space therebetween. Accordingly, the inner tank, the foam dam and the upper wall and side wall of the outer jacket form a sealed space that may be filled with the insulating polymer foam. The compressive sealing engagement of the dam between the tank and the jacket prevents the polymer foam from entering the lower portion of the annular space which includes the heating chamber and burner. U.S. Pat. No. 5,209,368 to Bradenbaugh is exemplary of this type of arrangement.
In the Bradenbaugh patent, the foam dam is a ring of polyurethane material that rolls down along the side of the inner tank as the jacket is positioned over the inner tank. In other prior art approaches, a slip agent such as talc is applied to the internal tank and the ring-shaped dam slips down along the internal tank as the jacket is placed over the tank.
The present invention relates to a liquid foam stop or dam for a tank assembly made from advanced materials that provide enhanced performance. Further, the liquid foam stop is wrapped around the inner tank at its desired position before positioning the jacket over the inner tank to thereby better ensure its proper positioning in the final product.